Electric lamp and discharge devices – Cathode ray tube – Plural beam generating or control
Reexamination Certificate
1999-06-17
2002-12-24
Patel, Nimeshkumar D. (Department: 2879)
Electric lamp and discharge devices
Cathode ray tube
Plural beam generating or control
C313S309000, C313S441000, C315S382000, C315S382100
Reexamination Certificate
active
06498427
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an electron gun for a color cathode ray tube, and more particularly, to a dynamic focus electron gun for a color cathode ray tube with improved electron beam through-holes for forming a quadrupole lens.
2. Description of the Related Art
An electron gun installed in a neck portion of a cathode ray tube emits thermions for exciting a phosphor layer. The performance of the cathode ray tube is influenced by the state in which the electron beams emitted from the electron gun land on the phosphor layer. Thus, electron guns for improving focus characteristics so that the electron beams emitted from the electron gun land precisely at a predetermined position of the phosphor layer and for reducing aberration of an electronic lens have been developed.
FIG. 1
shows an example of such a conventional electron gun for a color cathode ray tube.
The electron gun includes a cathode
2
, a control electrode
3
and a screen electrode
4
, which constitute a triode, first, second, third, fourth and fifth focusing electrodes
5
,
6
,
7
,
8
and
9
sequentially arranged adjacent to the triode and constituting an auxiliary electrostatic lens, and a final accelerating electrode
10
installed adjacent to the fifth focusing electrode
9
and constituting a main electronic lens.
As shown in
FIG. 2
, vertically elongated electron beam through-holes
7
b
and horizontally elongated electron beam through-holes
8
a
, for forming a quadrupole lens, are formed on an emitting surface of the third focusing electrode
7
and an entering surface of the fourth focusing electrode
8
, respectively. Also, as shown in
FIG. 3
, vertically elongated electron beam through-holes
8
b
are formed on the emitting surface of the fourth focusing electrode
8
and vertically elongated electron beam through-holes
9
a
are formed on the entering surface of the fifth focusing electrode
9
. Blades
9
c
inserted into the electron beam through-holes
8
b
formed on the emitting surface of the fourth focusing electrode
8
are formed at upper and lower edges of the electron beam through-holes
9
a
formed on the entering surface of the fifth focusing electrode
9
.
In the electron gun for a color cathode ray tube constructed as described above, since electron beam through-holes
7
b
,
8
a
,
8
b
and
9
a
must be formed within the limited diameter of a neck portion, the distance between electron beam through-holes is very small. For example, since the widths (w) of bridges among the horizontally elongated electron beam through-holes
8
a
are very small, i.e., 0.4~0.6 mm, these bridges are easily deformed by external forces.
Also, when a first quadrupole lens is produced, the vertical convergent force becomes weak due to the horizontally elongated electron beam through-holes
8
a
formed on the entering surface of the fourth focusing electrode
8
, a high dynamic voltage must be supplied to the electrode in order to attain a desired vertical focusing force. Also, since the blades
9
c
must be formed at upper and lower edges of the electron beam through-holes
9
a
of the fifth focusing electrode
9
, electrode fabrication is quite difficult.
An example of another conventional electron gun is illustrated in FIG.
4
.
Referring to the drawing, three electron beam through-holes
12
are formed on an emitting surface of a first focusing electrode
11
constituting a quadrupole lens, and a horizontally elongated electron beam through-hole
14
through which three electron beams pass is formed on an entering surface of a second focusing electrode
13
opposed to the first focusing electrode
11
and constituting the quadrupole lens together with the first focusing electrode
11
. A focusing voltage VF which is a static voltage is applied to the first focusing electrode
11
, and a dynamic focusing voltage VD varying synchronously with a deflection signal is applied to the second focusing electrode
13
.
In the above-described electron gun, since a single horizontally elongated electron beam through-hole (
14
of
FIG. 4
) is formed in the second focusing electrode
13
, the intensities, i.e., the magnifications, of the center and both ends of an electronic lens produced by the first and second focusing electrodes
11
and
13
are different. Thus, the sizes of electron beam spots Sanding on left and right sides of a screen become different, which causes a moire phenomenon.
SUMMARY OF THE INVENTION
To solve the above problems, it is an objective of the present invention to provide a dynamic focus electron gun for a color cathode ray tube which can lower the required dynamic focus voltage and improve the resolution of an image by preventing a moire phenomenon.
Accordingly, to achieve the above objective, there is provided a dynamic focus electron gun for a color cathode ray tube including a cathode, a control electrode and a screen electrode, which constitute a triode, a first focusing electrode having three vertically elongated electron beam through-holes formed through its emitting surface, a second focusing electrode which constitutes a quadrupole lens se together with the first focusing electrode and having three circular electron beam through-holes formed through its entering surface facing the emitting surface of the first focusing electrode, and a final accelerating electrode installed adjacent to the second focusing electrode and constituting a main electronic lens together with the second focusing electrode.
According to another aspect of the present invention, circular or regular-polygonal electron beam through-holes are formed on the first focusing electrode, and regular-polygonal or horizontally elongated electron beam through-holes are formed on the second focusing electrode.
According to still another aspect of the present invention, there is provided a dynamic focus electron gun for a color cathode ray tube including a cathode, a control electrode and a screen electrode, which constitute a triode, first and second focusing electrodes sequentially installed from the screen electrode, a third focusing electrode having vertically elongated electron beam through-holes formed through its emitting surface, a fourth focusing electrode having circular electron beam through-holes formed through its entering surface facing the emitting surface of the third focusing electrode and vertically elongated electron through-holes formed through its emitting surface, a fifth focusing electrode and having circular electron beam through-holes formed through its entering surface facing the emitting surface of the fourth focusing electrode, and a final accelerating electrode installed adjacent to the fifth focusing electrode, and wherein a static voltage is applied to the screen electrode and the second focusing electrode, a focus voltage higher than the static voltage is applied to the first and fourth electrodes, and a dynamic focus voltage varying synchronously with a deflection signal and equal to or higher than the focus voltage is applied to the third and fifth focusing electrodes.
BRIEF DESCRIPTION OF THE DRAWINGS
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Huh Woo-Seok
Kwon Yong-Geol
Lee Myeong-Hwan
Song Yong-Seok
Yun Kwang-Jin
Lowe Hauptman & Gilman & Berner LLP
Patel Nimeshkumar D.
Samsung SDI & Co., Ltd.
Santiago Mariceli
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